US3042198A

US3042198A - Method and apparatus for cleaning wood chips

Info

Publication number: US3042198A
Application number: US791196A
Authority: US
Inventors: Slavich Michael
Original assignee: United States Gypsum Co
Current assignee: United States Gypsum Co
Priority date: 1959-02-04
Filing date: 1959-02-04
Publication date: 1962-07-03
Anticipated expiration: 1979-07-03

Description

3,042,198 METHOD AND APPARATUS FOR CLEANING woon CHIPS Filed Feb. 4, 1959 M. SLAVICH July 3, 1962 2 Sheets-Sheet 1 &

METHOD AND APPARATUS FOR CLEANING WOOD CHIPS Filed Feb. 4, 1959 M. SLAVICH July 3, 1962 2 Sheets-Sheet 2 3,042,198 METHOD AND APPARATUS FOR CLEANING WOOD CS Michael Slavich, Pendleton, Greg, assignor to United States Gypsum Company, Chicago, Ill., a corporation of Illinois Filed Feb. 4, 1959, Ser. No. 791,196 6 Claims. (Cl. 209-44) This invention relates to a method and apparatus for cleaning wood chips or the like and more particularly to one in which a fluid such as water is used to effect a separation of waste material therefrom.

In the manufacture of fibrous products such for example as insulation board, hardboard and paper from lignocellulosic materials, a common source of raw material is chips obtained as a byproduct from the manufacture of lumber or from wood directly from the forest. It has only been recently, since the advent of the portable chipper, that it is possible to obtain chips directly from an operation in the woods. These chips, especially those made upon the portable chipper in the forest, both during their formation and in storage, accumulate a considerable amount of waste material such for example as rocks, dirt, scrap iron, wire, etc. Such waste materials are very detrimental to the machinery used in the manufacture of the above identified products. They quickly cause deterioration of grinder plates and plug up valves as well as tear the screens used in the formation of such sheet materials. While magnetic separation can be used to remove the iron particles, a substantial large percentage of these waste materials are nonferrcus in nature. It is therefore highly desirable that some commercially practical means he developed to remove as much of these waste materials as possible.

It is therefore an object of this invention to set forth a means of removing waste material, detrimental to the manufacture of fibrous materials, by a simple and novel means.

It is also an object of this invention to set forth a means of removing waste materials from chips in a continuous and efficient manner.

It is a further object of this invention to disclose a method of removing waste materials from wood chips by means of a continuous flow of water.

It is a still further object of this invention to set forth means to remove the material accumulated during the separation of such waste material from wood chips in a manner which will not interfere with the continuous operation of the apparatus.

It is an additional object of this invention to use riflies in a novel and facile manner to separate wood chips from waste by means of water.

It is an additional object of this invention to disclose a novel method for removing the water from chips and to recirculate the water for reuse.

It is a still further object of this invention to set forth a novel means for continuously removing and adding additional water so as to remove a portion of suspended material contained in the processing water.

Various other objects will readily occur to those skilled in the art of which this invention is a part.

This invention is best understood by means of drawings in which:

FIGURE 1 is an isometric side view of an apparatus following this invention,

FIGURE 2 illustrates one means of removing the ac cumulated waste material from the apparatus set forth in FIGURE 1,

FIGURE 3 sets forth an alternate means of removing the waste material from the apparatus illustrated in FIG- URE 1,

tates ate t FIGURE 4 is an enlarged sectional view through the line 4, 4 of FIGURE 1 and shows a riflle in greater detail,

FIGURE 5 is an enlarged plan view from FIGURE 1 and illustrates a spraying section, and

FIGURE 6 is a sectional view through FIGURE 5.

This invention is based upon the well known principal of the classification of materials of different densities by means of a fluid such as water. This method of separation is particularly adaptable to the removal of waste material from wood inasmuch as the wood will float while the waste material, being of a heavier density, will sink. It is the novel use of this method of separation which forms the basis of this invention.

In practicing this invention it is preferred to use a unique modification of the riflle type of classification or beneficiation. The chips and waste material are passed over a series of rifiies of special shape under a velocity and a degree of turbulence which will hold them in sufficient suspension to effect a separation. The velocity and degree of turbulence have been found to be critical for best results. Also it has been found that the shape of the riflle is of marked importance. The conventional type of rifl le in which the rifile bar is at substantially a right angle to the flow of material and to the bedof the trough in which they are enclosed, has been found to be highly unsatisfactory. It was discovered that with such a riffle that the chips would dam up in front thereof forming an inclined plane over which both the chips and a substantial portion of waste material passes. It was also discovered that if the rifiies, which can be made of steel, were inclined upwardly with respect to the bed of the trough in which they are placed and into the direction of flow thereby forming an acute angle with the bed that this accumulation of chips would not take place. The chips will be carried over the crest of the riffle and the Waste material will accumulate at its base. This angle was found to be critical; a range between about 35 to about 55 with the bed of the trough is satisfactory. It was also found desirable to incline the bed of the trough downwardly towards the discharge end. In the development of an apparatus, based upon the above principle, it was found that a substantial number of other factors are important. These will be referred to during the forthcoming description of this invention.

In practicing this invention I prefer to use the appara tus set forth in FIGURE 1, though it is not the intention to limit the scope of this invention to the particular device set forth therein. In the figure, 1 is a belt conveyor depositing chips, containing the waste material, into the chamber 2 which contains water under a high degree of turbulence. The water enters through a large pipe 3 at right angle to the Wall 4 of the chamber. The water, entering under high velocity, strikes the wall 4 thus causing the water to become highly turbulent. When the chips, containing the waste material, is dropped into this highly turbulent water the material is quickly suspended therein and discharged into the riflle section. Any extraordinary heavy mateiial such as nuts or bolts drop to the bottom and are not discharged.

As the suspended material passes through the trough 5, containing the riifies 6, the heavier waste material 7 accumulates at the base of the riflies and the chips float over the crest thereof onto the next. Note that the rifiles are inclined upon both the upstream and downstream side. These inclinations can be formed by the use of a steel angle with the terminating edges resting upon the bed as shown. It is not necessary that the angles upon both sides be equal. The trough containing the riflies is inclined downwardly towards the discharge end so as to assure a fast flow through the trough.

The efliuent from the riille section discharges upon the endless screen belt 8. This endless belt has its tail pulley 32 completely emersed in the tank 9 below the water level 10. The chips are carried up the inclined belt, over the head pulley ll, driven by any suitable means such -for example as an electric motor, not shown, and discharged into the bin 12. It has been found expedient to rubber coat these pulleys. The water level 10, in the tank 9, is maintained substantially constant by means of the float valve 29 which controls the introduction of fresh incoming water from the pipe 30 through the box 13 connected with the tank 9 by the conduit 31.

A portion of the waste material is finely divided and becomes suspended in the water. This accumulates to a marked extent and must not be permitted to build up to an excessive amount. In order to prevent this, a portion of the processing water must be removed from the system. This is accomplished by having a portion of the water discharge continuously through the weir-like opening 14 and into the trough 15 whence it is discharged as waste preferably passing through screens or the like, not shown, for reclaiming valuable fibrous material suspended therein.

The tank 9 may extend under a portion of the riffles and serves as a reservoir for the processing water. Water for reuse is removed from the tank through the inlet 16 by the pump 17 and recirculated to the chamber 2 through the opening 3, whence the process is repeated. A valve 18 is provided in the line leading into the opening 3 to control the amount of water added to the chamber 2 and hence the velocity of the water passing over the rifiles.

A portion of the water from the pump is preferably bypassed through the line 19 under the upper portion of the belt 3 and above the water level 10 for the purpose as will be subsequently set forth. A valve 20 is used to control the flow of water therethrough.

It will be found that a substantial amount of fibrous or chip-like material will pass through the openings in the screen belt 8. This accumulates in large quantities upon the surface 10 of the water in the tank h and must be removed. This is accomplished in a number of ways. One consists in passing water from the bypass 19 to the spray nozzles 21, situated between the top and bottom portion of the endless belt 8 and above the water level as shown in FIGURES 5 and 6. These sprays are directed in the direction of the tail pulley and against the material floating upon the surface. This causes the material to be forced through the space between the tank and the edges of the belt and upon the surface of the water above the belt where it intermingles with the effluent from the riffle section and may thus become entrapped with the dewatered chips leaving the system. A surprising number of fines are removed from the system in this manner for quite often the fines will become attached to a larger chip the second time and not pass through the screen again but will be discharged therewith.

Another means by which a portion of the material floating upon the surface can be removed is to place the surplus water inlet, which is the water level box 13, near the overflow or weirlike opening 14 so that a portion of the incoming water will readily flow to the overflow opening thereby removing any floating material between the two openings from the system. Some of the fresh water is removed immediately for this purpose but a substantial portion of it recirculates thereby supplying the excess to the system needed to remove a portion of the water containing the waste material suspended therein.

A still further means for removing the material floating upon the surface of the water in the tank and between the upper and lower portion of the screen, is to place the recirculating water inlet 16 for the pump 17 within the space between the screen belt and about a foot from the inside of the tail pulley and about a foot below the water level. A portion of the floating material is drawn in with the water and thus passes through the system again and possibly discharged with the dewatered chips.

Example of Operation The above and the following more detailed description of a specific example of an apparatus and its operation is supplied solely to provide a full, clear and concised means by which those skilled in the art to which this invention appertains may use it and is not to be construed as a limitation of the scope thereof. In this specific example, the trough is about 38 inches wide and about 18 feet long with a drop of about 8 inches in about 17 feet towards the discharge end. The riffles are formed from six inch angles of equal legs with their apexes upward thus giving an angle of 45 with the bed of the trough. This angle is preferred as it has been found to be very satisfactory. Seven such rifiles are used spaced about two feet apart. Water is introduced into the chamber 2 at about 1400 gallons per minute for about 740 lbs. of chips per minute. This is one gallon of water for about .5 lb. of chips. However this ratio is not too critical. The important factor is to have sufficient water to supply the degree of turbulence to properly suspend the material so as to effect a separation. An effective velocity of the water passing through the rifl'le section is about 1.6 ft. per sec. The amount of water above the riffle is usually between 2 to 4 inches.

The above apparatus removed about 75 lbs. of waste material from a days run of about 1,000,000 lbs. of chips obtained under regular operating conditions and hence is very effective in reducing the amount of damage to subsequent processing equipment.

The endless screen belt used to dewater the chips was made from a United States Steel Company, No. 36-3744 equalized wire belt having 36 mesh openings per foot of belt Width and 37 cross connecting rods per foot of belt length. The longitudinal spirals and the cross rods are of 14 gauge wire. The tail pulley is emersed in the tank and the head pulley placed above the water level of the tank and so positioned that it discharges into a bin for holding washed and cleaned chips as shown in FIGURE 1. The belt is about 20 ft. between the centers of the pulleys. As mentioned earlier, the water level is maintained constant by means of a float valve which introduces fresh water into the system to replace the water which is being continuously discharged through the opening 14 so as to remove a portion of the suspended material which has collected in the system. The amount of water leaving the system and hence that added depends upon how much suspended material it is desired to remove.

In order to provide a proper channeling of the effluent from the rifile section to the dewatering section, it is preferred to place a chute plate 33 at the discharge end of the trough for the passage of the effluent therefrom to the tank. The sides of the chute extend upwardly to prevent overflow and are convergent to facilitate its operation.

The size of chips used range from those which will pass a mesh screen to about 1" square with an average thickness of about though finer and larger sizes will readily pass through the system. Occasionally slivers 4 to 6 inches in length and 1 to 2 inches wide will be introduced; these have been treated satisfactorily.

Owing to the relatively large amount of finer size chips which have passed through the screen, it is desirable to use all the various means mentioned earlier for removing the material floating upon the top of the water within the tank and between the two portions of the belt. In the method of removing these finer size chips by means of the bypass water, it is not necessary that this water be introduced as sprays for the spray head can be removed and the water or fluid projected towards the tail pulley directly from the pipes, preferably at an angle of 45.

It is sometimes necessary to shut down the equipment for the removal of the waste material. This not only interrupts production but also results in an added operating cost which if it were possible to eliminate would effect a substantial operating savings. In order to prevent this interruption of production, it may be desirable to provide cleaning means to remove the accumulation of waste at the base of the riifles without the necessity of stopping the equipment. There are several ways by which this can be done. Two of which are set forth in FIGURES 2 and 3.

In FIGURE 2, there is shown at each terminating end of a riflle the chambers 22a and 22b each of which have a valve 23 at their lower ends to permit the discharge of the waste material which has accumulated. At one of the chambers there is provided a scraper 24 attached to a handle 25 extending through and beyond the Wall of the chamber. A suitable packing means is provided to prevent the escape of the processing fluid where the handle passes through the chamber. The operator occasionally pushes this handle thus causing the scraper to pass across the riffle and discharging any waste material which may have accumulated into the chamber 22a. As the handle is pulled back any waste upon the other side of the scraper is dropped into the opposite chamber 2211.

An alternate and less preferred means for the removal of the waste material, without the need of shutting down the apparatus, is illustrated in FIGURE 3. Here there is shown a receptacle 26 inclined towards a discharge 27 in the lower portion of the chamber. A valve 28 is provided to control the removal of the waste material from the chamber. Any waste material which will normally collect in front of the riflles will drop into this receptacle. When suflicient material has accumulated in the chamber, the valve 27 is opened and the solid material is allowed to discharge.

If this invention is properly carried out, such as in the manner set forth above, it will be found that substantially all of the damaging type of waste material will be removed. The remaining waste is usually small in size and seldom causes damage.

From the above description, it is apparent that some of the more important elements of this invention are: The introduction of the chips into an area containing a fluid such as water under a high velocity and turbulence to form a turbulent suspension, the passage of this turbulent suspension over riffles having their upstream faces in clined to the bed of a trough in which the riflies are positioned so as to form an acute angle therewith while resting thereon, the removal of the surplus fluid from the chips, the recirculation of this fluid again through the apparatus, and the addition of extra fluid so as to dilute the circulating fluid and thereby enable the removal of excessive fluid and hence permit the removal of some of the waste material held in suspension and also to simultaneously aid in the removal of fibrous particles which float upon the top of the fluid, in a tank used to hold the surplus fluid, by the passage of a portion of the extra fluid over the surface immediately through the opening for the discharge of the excess fluid. Useable fibers are removed from the fluid passing through the overflow. Also other means are used to remove the fibrous material floating upon the top of the tank.

While water is the preferred fluid media to effect a separation of the waste material from the wood chips, it is to be understood that any fluid which has a density greater than that of the Wood chips but less than that of the waste may be used for the purpose. Also this apparatus and process may be used to effect a separation of other fibrous from nonfibrous materials and to separate substances having densities greater and less than that of a fluid used for separating.

I claim:

1. A process for removing waste material from wood chips comprising passing said chips containing said waste over a series of spaced parallel disposed riflies inclined at an acute angle in the direction of flow while suspended in a liquid moving at a high velocity and uniformly thereover, said liquid having a density greater than that of the wood chips but less than that of the waste, whereby said waste collects at the base of said riflles and said chips pass over said riflies, removing all of the chips, except a portion of the smaller chips, from said liquid and recirculating at least a portion of the liquid containing said smaller chips over said riflies for ultimate entrainment with the larger chips being removed.

2. The process claimed in claim 1 in which said fluid is water.

3. An apparatus for removing waste material from wood chips comprising a trough, a series of spaced apart parallel riffles extending at substantially right angles across said trough and at an acute angle with the bed of said trough in the direction of flow, a chamber ahead of said trough and connected therewith, means for supplying a fluid in a turbulent state to said chamber, means for introducing wood chips containing waste material into said chamber for suspension in said fluid and for passage uniformly across an edge thereof into and through said trough and over said riflles at a high velocity whereby said waste material collects at the base of said riifles and said wood chips pass over the crest thereof, a tank extending beyond said trough for receiving the discharge therefrom, a moving foraminous endless belt conveyor for removing the said fluid from said chips, said conveyor extending below the fluid level of said tank for receiving the effluent from said trough thereon and above said level for discharging said chips away from said tank, means for recirculating said fluid, means for introducing fresh fluid into said tank, and an opening for removing a surplus of said fluid, said opening for removing said surplus fluid positioned adjacent said means for introducing fresh fluid whereby a portion of said incoming fluid washes a portion of said wood chips passing through said foraminous endless bed and floating upon the surface of said tank through said opening.

4. A process for removing waste material from wood chips comprising passing said chips containing said waste over a series of spaced parallel disposed riffles inclined at an acute angle in the direction of flow while suspended in a fluid moving at a high velocity and uniformly thereover, said fluid having a density greater than that of the wood chips but less than that of the waste, whereby said waste collects at the base of said riflles and said chips pass over said riffles, removing all of the chips, except a portion of the smaller chips, from said fluid and recirculating at least a portion of the fluid containing said smaller chips over said rifiies for ultimate entrainment with the larger chips being removed, introducing additional fluid with said fluid containing said smaller chips, maintaining a balance of fluid by removing an excess thereof along with any smaller chips which may have been suspended therein.

5. An apparatus for removing waste material from wood chips comprising a trough, a series of spaced apart parallel riflles extending at substantially right angles across said trough and at an acute angle with the bottom of said trough in the direction of flow, a chamber ahead of said trough and connected therewith, means for supplying a fluid in a turbulent state to said chamber, means for introducing wood chips containing waste material into said chamber for suspension in said fluid and for passage therefrom through said trough and over said rifl'les at a high velocity whereby said waste material collects at the base of said n'flles and said. wood chips pass over the crest thereof, a tank extending beyond said trough for receiving the discharge therefrom, a moving foraminous endless belt conveyor for removing the said fluid firom said chips, said conveyor extending below the fluid level of said .tank for receiving the efliuent from said trough thereon and above said level for discharging said chips away from said tank and means for recirculating said fluid, and means for removing small chips passing through said foraminous endless belt into the said tank and floating upon the liquid in said tank by entrainment with chips leaving the system upon the top of said conveyor.

6. Apparatus for separating Waste material from wood chips which comprises a chamber provided with means for introduction of fluid in a turbulent state, and with means for introducing wood chips contaminated with said waste material and exit means from said chamber communicating with an elongated trough downwardly inclined from said exit means, provided with a plurality of riffies located substantially normal to the long dimension of said trough and forming with the bed of said trough lying toward said exit means an obtuse angle, a tank positioned below the lower end of said downwardly inclined trough, an upwardly inclined foraminous conveyor positioned below the lower end of said downwardly inclined trough having its lower terminal portion within said tank and its upper terminal portion above said tank and be 8 yond the same in a direction away from said trough, and means for recovery from said fluid of small chips and the like which pass through said foraminous conveyor and collect in said tank.

References Cited in the file of this patent UNITED STATES PATENTS